Thermo-regulation of mammalian bodies has been of interest for a variety of health and medical applications, as well as general consumer uses. Warm-blooded animals, including human beings, maintain thermal homeostasis. That is, they are able to keep their core body temperature within a normal range, a near constant level, regardless of the ambient temperature of the surrounding environment. This can involve not only the ability to generate heat, but also the ability to prevent being over-heated and to cool down. Body temperature maintenance incorporates a wide range of different techniques that result in a body temperature continuum. For example, typically, warm-blooded animals control their body temperature by regulating their metabolic rates (e.g. increasing their metabolic rate as the surrounding environmental temperature begins to decrease), such as through shivering when the ambient temperature becomes too cold. Additionally, when the body becomes too hot, humans perspire as another several safety features that help to regular the body's normal temperature. If the body is unable to maintain a normal temperature, hyperthermia or the opposite condition, hypothermia, can occur.
Body temperature regulation is an important parameter for patients who undergo surgery or during post operative recovery. Human body temperature can fluctuate temporarily due to various factors, such as age, physical activity, illness, or emotional stress, normal body temperature is 98.6° F. (37° C.) when the body is at rest. Studies have demonstrated that maintenance of a normal or relatively warm patient body temperature during medical procedures can minimize the likelihood of post surgical infections or other complications, and help the patient heal more quickly, thus shorten hospital stays (e.g., Woo Y J, Atluri P, Grand T J, Hsu V M, Cheung A. “Active Thermoregulation Improves Outcome of Off-Pump Coronary Artery Bypass,” Asian Cardiovasc. Thorac. Ann. 2005, 13:157:160; Mahoney C B, Odom J. “Maintaining Intra-Operative Normothermia: A Meta-analysis of Outcomes with Costs. AANA J. 1999, 67:155-163). For a healthy human being, normal skin temperature around the body core is about 35° C., and the skin temperature of the arms and legs typically may range from about 31-33° C.
Regulation of an infant's body temperature is another parameter of interest for healthcare professionals, parents, and other caregivers. The normal axillary temperature of a newborn infant may range from about 36 to 37.5° C., after measuring for about 5 minutes. Because neonatal babies typically are not able to regulate their body temperature as well as older children or adults, they easily may become either cold or overheated which can lead to a variety of health problems (hypothermia, heat exhaustion, etc.). Hence, it is not wise to either cover or overdress them on warm days or underdress them on cold days. With such little skin surface, infants lose heat or overheat fast. Premature babies, in particular, are susceptible to temperature fluctuations, and are typically housed in incubators and monitored closely to ensure that they are kept sufficiently warm without overheating. A caregiver would want to know whether the infant was too cold, or at the other extreme a caregiver would wish to be able to monitor the temperature of a feverish infant. A fever temperature of 100.4° F. or greater can be dangerous and should be reported to a doctor. Similarly, the elderly are another population that may be susceptible to difficulty regulating their body temperature, especially with respect to overheating.
A temperature sensitive composition that communicates a relative response by means of a visual indicator can be incorporated into certain protective articles, clothing or garments. Nonwoven fabrics have been treated with thermochromic pigments to provide a visual indication of a shift in temperature through color change. In many cases, the thermochromic pigments are coated onto the fibers or fabric using a multi-step topical application method. However, topical application may lead to color flaws in the surface of the fabric if the coating is not uniformly applied, along with the additional cost of a post-treatment step. Certain attempts have been made to overcome this problem. U.S. Patent Application Publication No. 2003/0087566 to Carlyle, et al., for example, describes a method for uniformly incorporating a thermochromic pigment into a melt-spun fabric by incorporating it into the polymer melt at the time of fiber or filament formation. However, the method of Carlyle, et al. still lacks the desired level of control over the thermochromic characteristics of the resulting fabric in the range of ambient to body temperature.
As such, a need currently exists for an improved method of using a thermochromic material, such as a nonwoven web, fiber, or film in an application for monitoring the relative temperature of a body or its immediate ambient environment. Currently an unmet need exists for a device, method or system that can help caregivers monitor relative body temperature. Such a device or method would be a helpful and appreciated tool for either patient or child care uses.